Percussion sensitive pyrotechnic or pyrophoric alloy-type priming mixture



United States Patent O PERCUSSION SENSITIVE PYROTECHNIC R PYROPHORIC ALLOY-TYPE P R I M I N G MIXTURE Donald S. Foote, Greens Farms, and Richard A. Sahlin,

Fairl'ield, Conan, assignors to Remington Arms Company, Inc., Bridgeport, Conn., a corporation of Delaware No Drawing. Filed June 1, 1964, Ser. No. 371,813 3 Claims. (Ci. ll4-38) This invention relates to the production of percussion sensitive explosive compositions having particular utility as priming mixtures for ammunition.

A substantial number of pyrophoric alloys are known which may be identified generally as those alloys which on being struck or abraded will have fine particles released therefrom which will spontaneously ignite in brilliant sparks capable of igniting gases, alcohol, naphtha, and other inflammable substances. Such alloys find their Widest use as flints for cigarette lighters, miners lamps, welders torches, etc. Probably the most widely used of such alloys include as their principle active ingredients metals of the rare earth family, such as cerium, lanthanum and others, frequently modified by the addition of iron, magnesium or other metals, to vary the nature of the sparks produced, hardness or other properties. One of the commonest of these rare earth alloys is known as misch metal, .the exact composition varying somewhat With different manufacturers. Other known pyrophoric alloys contain one or both of the active metals titanium and zirconium alloyed in various combinations with lead, tin, aluminum, antimony, manganese, bismuth and silicon. A common characteristic of these alloys appears to be that when finely divided fresh clean surfaces are produced in air or in contact with other oxygen bearing media, the alloy ignites spontaneously. Some active metals appear to form protective oxide films so rapidly when a clean surface is exposed that no substantial reaction takes place and these are not considered to be pyrophoric metals. Aluminum is an outstanding example of this effect. For use in percussion priming mixtures, it is also necessary that the alloys have such characteristics of strength and brittleness as to fracture readily and produce clean reactive surfaces under the action of a firing pin below.

We have discovered that virtually any of the pyrophoric alloys which are sufiiciently active to be used efiiciently as lighter flints can be used in admixture with active oxidizers to produce sensitive priming mixtures which will react with explosive violence under the stimulus of percussion.

Since none of the essential constituents of such a mixture are of themselves explosive, it follows that such mixtures are safer to prepare and to handle in a primer manufacturing operation than are the conventional fulminating explosive heretofore used.

An added and unexpected advantage of such primer mixtures is their extraordinarily high degree of stability when exposed to elevated temperatures for extended periods of time.

For some applications it may be desirable to modify or to sensitize the mixtures by the employment of explosive ingredients such as l-guanyl-4-nitrosoaminoguanyltetrazene commonly known as tetrazene or tetracene. But even when so modified, the mixtures are still far safer to handle than mixtures employing the conventional initiating explosives. Similarly auxiliary fuels, frictionators, and other primer modifying expedients may be resorted to in accordance with principles known in the explosives art.

The exact nature of the invention will become more apparent from consideration of the following specification in which there will be discussed in order (1) the suitable and preferred pyrophoric metals, (2) the suitable and preferred oxidizers, (3) suitable ingredients for modifying the sensitivity and other characteristics of the compositions and (4) an illustrative group of priming mixtures employing these ingredients.

PYROPHORIC ALLOYS In general, a pyrophoric alloy has been defined as one which has the property of emitting sparks when scratched or struck with steel and such active pyrophoric alloys as misch metal are widely used as flints in lighters and other igniting devices for gases. Misch metal has been defined as a pyrophoric alloy which consists of a crude mixture of cerium, lanthanum, neodymium and other rare earth metals in the approximate ratio in which they occur in monazite sand and misch metal is usually obtained by electrolysis of a fused mixture of the chlorides of these metals. Although the specific composition of misch metal may vary somewhat with the producer, a typical composition is as follows: Percent Cerium 50 Lanthanum 40 Other rare earth metals 3 Iron 7 TABLE I.PYROPHO RIC ALLOYS Zirconium 25 25 Titanium 45 45 Lead 45 45 Antimony. Manganese Magnesium Misch met Ir With some modifications in specific primer composition, it is felt that the above or any other pyrophoric alloy exhibiting the characteristic of emitting showers of sparks when struck or abraded can be used.

In general, it is preferred to use the in granulations of such size that all passed through a 250 mesh screen.

OXIDIZERS Satisfactory performance of pyrophoric alloys in percussion primers requires that they be used in combination with active oxidizing agents. Barium nitrate (B'a(NO has been used as the main oxidizer in most of the experimental work, with lead dioxide (PbO used as a more active supplemental oxidizer to improve the igniting efficiency of the mixtures. Other oxidizers which can be used for some purposes include potassium perchlorate (K010 and red lead oxide (Pb O potassium chlorate, (KClO and lead nitrate (Pb(NO The latter tWo particularly are less desirable than barium nitrate and lead dioxide because of corrosive effects and because of pyrophoric alloys particles may be 3 solubility in water, which tends to reduce the stability of the resulting primer mixture in long term storage under possible adverse moisture conditions.

ADDITION AGENTS AND TECHNIQUES FOR MODIFYING PRIMER MIXTURES Although the essential elements of a pyrophoric primer as prepared in accordance with this invention are an active pyrophoric alloy and an active oxidizing agent in an intimate mechanical mixture, various modifications may be made to such a mixture to improve its storage stability, sensitivity, igniting power and other characteristics. Similarly, there are various handling techniques which may be employed in the production of the mixture which modify the characteristics of the mixture.

Among the measures which may be adopted to modify the igniting characteristics of the resulting priming mixtures are the addition to the mixture of various fuel supplements with appropriate adjustment of the oxidizer content of the mixture to maintain a satisfactory oxygen balance in the mixture. Suitable fuel supplements include finely divided powders of active metals such as magnesium, titanium and zirconium, hydrides of such metals, such as titanium and Zirconium hydrides, and other fuel supplements, such as antimony sulfide, calciumsilicide, and sulfur. In addition to modifying the ignition characteristics of the mixtures, some of the materials mentioned above, such as zirconium and zirconium hydride, had the effect of increasing the sensitivity of the mixtures to percussion initiation probably because they are used in a fine powdered form which is so readily ignitible.

The effect of zirconium and zirconium hydride as sensitizers has been mentioned above. In addition, particularly where high sensitivity was required and high temperature stability was not a factor, it has been found that the addition of tetrazene, sometimes called tetracene (1-guanyl-4-nitrosoaminoguanyltetrazene) to the mixture has a desirable sensitizing action, as it has in other known priming mixtures.

Storage stability of these mixtures is in general satisfactory although the chemical activity of all of the ingredients must be considered. Those mixtures containing only powdered pyrophoric alloys and inorganic oxidizers with no ingredients which are by themselves explosive are particularly stable when exposed for long periods at high temperatures (e.g., 6 hours at 500 F.).

The chemical activity of some of the active alloys considered has produced problems relative to stability under humid storage conditions or relative to use of such mixtures for wet charging or for dry charging with water or alcohol soluble binder solutions. These problems can usually be overcome by the use of binders which include neither alcohol or water, such binders being selected from those which are compatible with the active alloys and which are soluble in hydrocarbon solvents which are themselves compatible with the active alloys. For example, rubber cement dissolved in heptane appears to be a suitable binder. It has also been found that an alloy having substantially the proportions of 80% misch metal as hereinbefore defined and 20% magnesium can be stabilized by ball mill grinding, while submerged in heptane, for extended periods of time until the material is reduced to finer particle size than 325 mesh. This material appears to be stable even when employed in wet mixtures, stored under humid conditions or used with water-soluble binders or binders of shellac in alcohol. Polyacrylamide and/ or silicone waterproofing agents in hydrocarbon solvents also function as compatible binders.

PRIMING COMPOSITIONS Typical mixtures yielding reasonably satisfactory performance in powder ignition are tabulated below, With their sensitivity compared to standard products.

Table II relates primarily to the priming mixtures comprising the titanium-zirconium base pyrophoric alloys and Table III relates primarily to the priming mixtures comprising the misch metal based pyrophoric alloys.

In each of Tables H and III the sensitivity of the primers prepared with these mixtures is compared to the sensitivity of commercial lead styphnate priming mixtures loaded in the same type primer. The sensitivity values are tabulated as X in inch ounces which is the energy level at which of the primers in a given sample lot fire in a conventional free drop test machine.

TABLE II.-PRIMING COMPOSITIONS, TITANIUM-ZIRCONIUM BASE ALLOYS PY-3 PY-l2 PY-17 PY-Zl PY-29 Pyro Alloy:

43 Ti, 47 Pb, 10 Sn 25 Ti, 25 Zr, 50 Sn 35 Zr, 35 Pb, 27 Mo,

Potassium perchlorate Barium nitrate Lead dioxide Zirconium (coarse) Zirconium (-325 mesh) PE Sensitivity: 1

N0. 72 Primer No. Primer 1 Commercial lead styphnate mix. 2 i in inch ounces.

TABLE IIL-PRIMING COMPOSITIONS, MISCH METAL ALLOYS P Y-66 P Y-76 PY- P Y-95 Pyro Alloy:

-75 misch metal and 25 Fe 80 misch metal and 20 Mg 80 misch metal and 20 l Potassium perchlorate Barium nitrate- Lead peroxide- Zirconium (coarse) Zirconium (-325 mesh) Antimony s Tetrazene Sensitivity, N0. 70 Primer 30 9 1 Commercial lead styphnate mix. 2 i in inch ounces.

Many variations in mixtures may be made without departing from the teachings of this invention. Accordingly, the invention is not to be construed as limited to the specific examples above but only as defined by the claims appended hereto.

We claim:

1. A percussion sensitive ammunition priming mixture which comprises as its essential ingredients in an initimate mechanical mixture from about 25% to about 60% of an active pyrophoric alloy and from about 40% to about 70% of an active inorganic oxidizing agent selected from the group of active inorganic oxidizing agents consisting of barium nitnate, lead dioxide, potassium perchlorate, red lead oxide, potassium chlorate and lead nitrate.

2. A percussion sensitive ammunition priming composition which comprises an intimate mechanical mixture of a finely defined pyrophoric alloy and a finely divided active inorganic oxidizing agent selected from the group of active inorganic oxidizing agents consisting of barium nitrate, lead dioxide, potassium perchlorate, red lead oxide, potassium chlorate and lead nitrate, with a binder medium which is not chemically reactive with the pyrophoric alloy under any normal conditions of storage.

3. A percussion sensitive ammunition priming composition as defined in claim 1, including as an explosive sensitizer l-guanyl-4-nitrosoarninoguanyltetrazene commonly known as tetnazene or tetracene.

4. A percussion sensitive ammunition priming composition as defined in claim 1 in Which said oxidizing agent comprises a mixture of barium nitrate and lead dioxide.

5. A percussion sensitive ammunition priming composition as defined in claim 4 said barium nitrate being present in about twice the amount of lead dioxide included in the mixture.

6. A percussion sensitive ammunition priming composition as defined in claim It in which substantially 31% of a powdered pyrophoric alloy of misch metal and mag nesium is in admixture with substantially 45% of powdered barium nitrate, substantially 20% of powdered lead dioxide, and substantially 4% of a sensitivity modifying agent.

7. A percussion sensitive ammunition priming composition as defined in claim 6 in which said composition includes as a binder medium a rubber cement utilizing heptane as a solvent.

3. A percussion sensitive ammunition priming composition as defined in claim 6 in which l-guanyl-4-nitrosoaminoguanyltetrazene is used as a sensitivity modifying agent.

References Cited by the Examiner UNITED STATES PATENTS 1,974,015 9/1934 Decker et al. 14937 X 2,421,029 5/1947 Magram l49-37 2,560,452 7/1951 Kerr et al. 149-37 2,942,546 6/1960 Liebhafsky et al. l49-43 X 2,988,876 6/1961 Walden 14943 X 3,090,310 5/1963 Peet et al. l4943 X BENJAMIN R. PADGETT, Primary Examiner. 

1. A PERCUSSION SENSITIVE AMMUNITION PRIMING MIXTURE WHICH COMPRISES AS ITS ESSENTIAL INGREDIENTS IN AN INITIMATE MECHANICAL MIXTURE FROM ABOUT 25% TO ABOUT 60% OF AN ACTIVE PYROPHORIC ALLOY AND FROM ABOUT 40% TO ABOUT 70% OF AN ACTIVE INORGANIC OXIDIZING AGENT SELECTED FROM THE GROUP OF ACTIVE INORGANIC OXIDIZING AGENTS CONSISTING OF BARIUM NITRATE, LEAD DIOXIDE, POTASSIU PERCHLORATE, RED LEAD OXIDE, POTASSIUM CHLORATE AND LEAD NITRATE.
 6. A PERCUSSION SENSITIVE AMMUNITION PRIMING COMPOSITION AS DEFINED IN CLAIM 1 IN WHICH SUBSTANTIALLY 31% OF A POWDERED PYROPHORIC ALLOY OF MISCH METAL AND MAGNESIUM IS IN ADMIXTURE WITH SUBSTANTIALLY 45% OF POWDERED BARIUM NITRATE, SUBSTANTIALLY 20% OF POWDERED LEAD DIOXIDE, AND SUBSTANTIALLY 4% OF A SENSITIVITY MODIFYING AGENT. 